Taps, dies, and the like



4 Sheets-Sheet .l

F.IIIIII ...LPv IHUMM ttf/6.

June 23, 1925.

P.A KREUTZBERGER TAPS, pms, AND THE LIKE und Aug. 23, 1921 Immer/tol l.f.f.ney;tzb cran' P. KREUTZBERGER TAPS, DIES, 'AND THE LIKE June 23,1 1925.

Filegug. 25, 192i 4 SheetsSheet 2 Invent-azz. 13. Ifr e U/z bergen 4 Sheets-Sheet 5 A B :alli ID June 23, 1925.

P. KREUTZBERGER TAPS, D11-is AND THE LIKE Filed Aug. 25. 1921 lum,

June 23, 1925.

P. KREUTZBERGER TAPS, DIES, AND THE LIKE ilileudvAug. 25, 1921 l 4 Sheets-Sheet 4 Patented `lune 23,192.5. Y I i i UNITED STATES PATENT oFFlcE. 'y I PAUL xBEU'rzBEaEB., or BELLEVUE,

Tus, mns, AND THE mE. i p

Application; ma August as, 1921. serial mi. 494,563.

To aIZZ' whom it may concern.: Fig. 7,'indicates the shapeH of a tooth of Be it known that I, PAUL KBEUTZBERGER, the tap, shown in Fig. 6 after the milling a citizen of the French Republic, and' reof the grooves to form the front" cutting .50h

siding at 8 Rue des Buttes, Bellevue, Seinef surfaces, et-Oise, France, have invented certain new Fig. 8 illustrates` the backing-'oit of "the and useful Improvements in andlelating teeth, v to Taps, Dies, and thel like, of Vwhich the Fig. 9 illustrates the completedltap to a following is a specification. y larger scale, Y. A.

The present invention relates to improve- Fig. 10 indicates the original screw thread 10 ments inv tools used for forming triangularly corresponding to the ntap shown in Fi-g. 5, shaped' threads of screws or of nuts, either shown -as'developed on a plane surface, truncated or not, such as are used in taps Fig. 11 indicates the screw thread shown and dies. The invention particularlyrein Fig. 10, firstly after the tapering of the 60 lates to such tools in which the cuttin of thread, and secondly after the milling of 15 the metal is effected on onefside only o the the grooves to form the front cutting cutting teeth; The tools thus formed resurfaces, .c quire less effort to bring them into action, v Fig. 12 indicates the screw' thread shown theyvwear slower and may have a'smaller in Fig. 11, after the backing-o operation, 05 length than those generallyused because Fig. 1,3 shows a modified forni of tap in their mode of action is such as to allow all which the grooves forming the front cutthe elementary cutting edges to operate with ting .teeth ,are milled as slightly helical the best clearance angles. grooves.l

The present invention consists in an im- In'. order that the operation ofthe tools '(0 proved construction of screw cutting tools may be clearly understood, it will now be of the type in which the teeth only cut on explained how a single lathe tool may be one side, the improved construction being operated so as to ycut on one side only.

such as to facilitate manufacture. This method'of working in the case of an The accompanying Figures 1 to 12 clearlyI ordinary single -tooth screw-cutting lathe 'lli` illustrate how the improved tools, forming tool-is known. n the subject of the present invention, are Fig. 1 is a section of aform of screw used and constructed in practice. y thread which for instance may conform to Fig..1 illustrates the usual cutting action the international standard system of screw of an ordinary lathetool,

AFig.2 illustrates the cutting action of an nite; size. r ordinary lathe tool when arranged to cut When an ordinary single tooth screwon one side only, cutting tool is used in a manner analogous Fig. 3 diagrammatically illustrates a tothe operationof the taps and dies, which chasing tool in which the cutting action is cutfon one side of the teeth only, then in- 85 analogous to that of the improved taps and stead of'eifecting an advance of the .toolin 40 dies, constituting the invention, the direction of the arrow F, that; is perv Fig. 4 illustrates the cuttlng action-of the p'endicularly to wand ftherefore also teeth of the chaslng tool shownvln Fig. 3, perpendcularly to the.. axis of the' screw threads, with a truncated part B C, of dei- 80 Fig. 5 shows a tap in process of man uformed, the advance is eiected as shown in 90L facture after the usual 'screw threading op-vv Figure 2, in the direction of the arrow '-F., eration has been performed,` that is in a direction parallel to the oblique Fig.' 6 shows the tap 1llustrated 1n Fig; face 'C D,.which is on that side of'its re- "5 after the thread has been tapered, maining metal screw thread corresponding easily understood.

In the case of` Figure 1, the part C D of the tool works with a negative cut as regards its front face as a scratcherworks,

whilst in the case of Figure 2, the inclination 'of the thread of the screw, has the efL giving a natur of the single tool.

Other differences not so. importantl could be pointed out, and experience has shown that the cutting action illustrated in Fig` ure 2 is much preferable to the cutting action shown in Figure l.

The `chasing i001 illustrated in Fig. 3

comprises a combination of multiple tools whose cutting action is the same as that of the single tool above described.

In this chasing tool which is only dia` grammatically illustrated, the elementary tools A1 B1 D1, A2B2 D2, A3 Ba D3, ABCD have sections Lof 'increasing dimension V4con- ,seen that if a sidered from the geometrical point of view,

as shown on a larger scale in Fig. 4 by cut-.

ting the section of the completescrew-thread a b c d by a series of lines I, II, III, IV, Aall of them parallel to a b. It is, easily 5 chasing tool thus constructed is, as stated above, displaced from right to left, with the same speed relatively to the speed of rotation of the spindle of the lathe -as that of an ordinary single tooth screw cutting tool, the various elementary tools or teeth of the chasing tool will cut shavings, the sections of which are shown by the spaces comprised between consecutive,..lines, such as I and II, II and III, III and IV; the elementary tool A3 B8 Da will deliver turnings the section o which 1s the portion comprised between the lines II and III of Figure 4. The sections of the various successive shavings are shown by hatchings alternately drawn in opposite directlons, in order to be more clearly seen.

It is obvious that when Ythe last teeth of the chasing tool, whdse shape conforms exactly to ABCD reaches .the piece to be screwthreaded, the latter will be acted upon in one cut only,l such cut taking place under the bestworking conditions as diagrammatically illustrated in Fig. 2 and set forth above. v u

In workshop practice, means are known,

al cut tofthe part Av B the thread of the screw, such asl operated either by hand or mechanically, for suitably shaping a tool, the section of which is polygonal, such asthe section of the chasing tool which has just been described. It can, therefore already be considered that the description of the saidA tool is suhcient for permitting its construction.

In thecase of a Screw-tap or a die formed in a similar manner to the chasing tool above described and having for instance four substantially radial cutting faces, each of the latter will act like the chasing tool; the chasing tools will however be displaced, relatively to each other ,in the same manner as two consecutive teeth of one and the same chasing tool, so as to cause all the elementary tools which are available, to Work equally. In this case, the manufacture of the tool is preferably effec-ted by meansof a process similar to that which will now be particularly described by way of example. Y

For greater simplicity in the figures, the case of atap will be considered.

The round bar of tool steel from which 'the tap is tol be made having been turned to a suitable` diameter, it is necessary to Iscrew-thread according.` to the ordinary methods, then before milling the grooves which form the cutting surfaces, to proceed with the following operation Against the whole length of the tap is placed a suitable chasing` tool having n' threads, n being the number of threadsl that are intended to( cut simultaneously, not counting the lfinishing threads, that is the threads of full section. The teeth of this Vchasing tool fit perfectly in the section of the screw-thread of the tap in its present form after screw threading, .but before milling, as shown in Fig. 5. Then there is. given to the chasing'tool an advance movement from the right to the left (for a righthanded screw-thread 'and a normal direction of rotation of the lathe) with a speed or pitch p1, where f p being the pitch of the screw-tap to `be made. It Lwill be easily understood that the said chasing tool will leave behind it a screw-thread which decreases until it disappears entirely when thespindle of the lathe has made vn+1 turns, thus forming the shape illustrated in Fig. 6. After lthis will be performed theprocess of milling the grooves forming the front cutting surfaces.

It should be pointed out here that according to the principle of this invention.'only the left hand edge of each of the teeth A1 B1, A2 B2, A B should cut; at present, the said face which is behind it would foul the surleft hand edge cannot cu-t because the surface of the thread just generated by the said edge, as the surface projects relatively to the said edge as shown vin Fig. 7 by thel edge A B and thesurface behind it.- It

' remains therefore, toproceed to an operation of backing oli, giving the necessary clearance to the said surface behind 'the cuti ting edge.

Aio

- ordinary taps and dies. With this object an The said operation is elected by a screwthreading cut in contradistinction to what is effected in the .backing-off operation of ordinary screw-cutting tool is placed exactly against A1 B1 Ahaving its cutting edge inclined at 60 to the axis to correspond with the line A B and having its cutting surface directed downwards in contradistinctionvto I i. the ordinary lposition. By rotatingl the lathe in the ,dlrection opposite to its`or dinary direction of rotatlon, the said tool will cut the surfacesto be cleared. Alternatively the chasingtool'illustrated in'Fig'.

3 may be substituted forthe screw-cutting tool. If an -advance or pitch is given to the tool which is greater than the pitch p of the screw-thread for which the tap is constructed'. it will cut the above surface behind the cutting edge in such a manner that after manu-`v ',facturemvhen thetap comes to be-used, the

edge A1 B1 will have the necessary back clearance and will be capable of cutting the metal without fouling (Figures 8 and 9).

However, if the said tool continuesits i,lr'lotion'under' the same conditions, it would cut the edges A2 B2, v 1 Bs, in such a manf ner as to completely destroy the stepped ar= rangement ofthe successlve teeth, which `isitself a ,necessary feature of the present invention. In order to cause the said tool, therefore,

to carry out behind the edge A2 B2, the same As the pitch corresponding to the 'advance 'ofthe said' tool is greater than Ap, it must rbe a fortioriv greater than p1and may be expressed by p1 (I -I-). `The quantity a: de-

the clearance which iszto beefi Figures 10, 11 and 12 which4 show a porpends on In'the case of a'screw-tap with'four front cutting-surfaces, then in order to bring' the. tool against the face Az B2, it will be necesl s'ary to impart .to itl a recoil equal to Thetime chosen during which to effect the said recoil, will of course be chosen so that the tool. is then opposite one of the grooves consecutive rows of-teeth, at w ic h time there is an empty space through which thetool can move The meth. d of carrying but this processq. may vary according to' the arrangements ofthe lathe... One` such method will now be described for lthe sake of example. f First o al1,'jthe`- movement of pitch lequal to (Li-m) p1 may be obtained by means of f Y themain screwof the lathe, and the recoil may be elfectedl by the screw of the small upper carriage ofthe llathe, it 'being understood that the slideway of,Y the small carriage is maintained parallel to the geometrical axis ofrotation ofthe lathe.

.With this method, it will be sufhcient to.

mount a pawl to actuate the said screw of the small carriage, the said pawl acting in thel suitable direction with a suitable amplitude four-timesper revolution at the time when the tool comes into the empty space -formed by one of the four-grooves of the tai).

as applied to the present vbacking V-off yproc- "ess, an important improvement. f1it11s to be understood that ythis backingolf opera- The jerkingmoveinent thus produced is, i

tion in thecase of^a large screw-tap-may be effected in several cuts, in the last of whichv it nlioves'exactly in the path "hereinbefore described. The clearance thus obtained is correct for the first n threads, the teethvof which operate in oblique graduated cuts,'as above described.y At its right hand end, the tap has, in addition, a number of vfinishing teeth, the section of which corresponds exactly to the screw-thread to be-made.

I t is possible mshi teeth by giving to the main carriage o the lathe' a continuous speed corresponding to a. pitch equalfto p (l-i-) .and

'to zolnpletelyi haakte these i not p1 (Li-(v), While the intermittent superimposed displacement or'recoil is made l of amplitude equal toy instead of But, as a -more-v simple operation, it is `possible to continue for, the said `finishing screw-threads, the cut or cuts carried. out on the first 'nl screw-threads. `In this way,

the saidi finishing teeth will be less and less cleared from the rear,`bit this has no serip ous drawback. Y Various phases of manufacture of a screw-tap vembodying the improvements of the ,present ginvention, are illustrated iny 1 tion of the 'screw-threaded developed into I passage of the chasing tool, while the right A hand side of this figure -shows 'the sameI screw-thread interrupted by the milled grooves of the screw-tap.

Lastly, Fig. 12 shows a finished screwtgrad backed olf behind its cutting edges rlhe broken line A a, a1 a2 A a a1 a2 represents the path of the tool used for yVe'ecting the backing off. The part a1 a2 of the said path corresponds to the recoil motion l of amplitude equal to 24E previously referred to..V

It has been stated above that a tool, which works in the manner diagrammatically illustrated in Fig. 2, as is the case with' the tools forming the subject of the present invention, possesses a natural cut along its active edge A B, on account of the inclination of the helix forming its path.`

wWhen cutting the usual screw threads the said inclination is small, and therefore, the cutting action of the tool is not much improved thercby.

lt may be advantageous in certain cases to increase the front clearance angle of the' said tool, and this may be effected, for ex-v ample, in the case of a tap such as is indicated in Fig. 4 by substituting for the ordinary milled rooves which are straight and parallel to t e axis of the tap, helicoidal grooves the pitch of which has the same direction as that of the screw-thread, but is much greater than the latter as shown in Fig. 13.

The'method of manufacture will under these conditions be altered as follows l The operations which `are illustrated in Figs. 5 and 6 and described above being finished, the grooves are milled along a path of large pitch (to the right for a right-hand screw-thread and to the left for a lefthand screw-thread). In order that the edges A1 B1,`A2 B2, A B, shall in all cases be rectilinear, it is necessary and sufficient that the cutting surfaces thus milled should coincide with the surface of a screw having a triangular thread of the same angle as that of the screw-thread but with a greater pitch P, or in other words, that the milled cutting surface must be an oblique helicoid, the generating line of which makes with the axis, the same angle as thegenerating line of the hlicoid forming the active cutting side of the actual screw-thread of the tap.

For the most usual case when the section of the screW-thread-is an equilateral triangle, the milling cutter will have a shape which approximates to that of the milling cutters used for cutting' twist-drills or socalled American drills. Tools of this kind have in fact been made for cutting helicoidal which has been l name to this specification.

eration is veffected as above described, except that the amplitude of the recoil movement which previouslywas for a tap with four cuts becomes now This may be proved by means of simple geometrical considerations by drawing the development on a plane of the directing helices of the helicoids having pitches p1, p1. (1+) and P respectively.

rlhis result is extremely important for the reason that when backing olf is effected by means of a radial as distinct from a helicoidal action, the manufacture of taps in which helicoidal grooves form the front cutting surfaces presents considerable diiiicultles.

As stated above, the present backing off methods apply equally to taps having straight. or helicoidal ooves. The above description refers partlcularly to taps, but it may be applied in great part to dies, the diderence being that the latter have internal instead of external cutting surfaces.

1. 'An improved screw cutting tool of the type of taps, dies and the like comprising a series of teeth, in which similar sides, one on each tooth, are formed as cutting (front) edges and all lie on a first common screw surface, while the opposite set of similar sides, one on each tooth, is formed with noncutting (back) edges, and all lie on a second common screw surface, the non-cutting edges being such that each surface formed by the back of a tooth and passing through one of the said edges coincides with the said second common screw surface; while the cutting edges are such that the surfaces formed by the backs of the teeth and passing through the said edges are screw surfaceshaving a common pitch which is greater than that of either of the said common screw surface, the screw surfaces for consecutive teeth being axially displaced with regard to one antool of the type -of v front cutting surfaces are in contradistinction yhelical surfaces so as to increase the front clearance angle of the cutting edges of the teeth.

ln testimony whereof I have signed my PAUL KREUTZBRGEB. 

